I had a Racer Brown STX21 in a 340 I had in my Duster back in the late 70s which was a flat tappet solid lift cam. It had 0.560" lift but I don't remember the spring pressures. I had rocker arms and pushrods from a 273 in it and never even thought of rocker arm geometry back then. Everything held up to 7000 rpm launches and shifts although I did bend a pushrod when I blew a gear once. I was able to keep moving it up in the hole and applying pressure to get it bent back straight enough to get out without removing the intake. I put a stock replacement TRW pushrod in it's place and it was off to the races again with no problems. Fun days going fast but probably could have gone faster having everything optimized.
